How to create material design like custom scrollbar with numbers and alphabets bubble in recylerview

In many new android applications and their latest update those applications(mostly material design) have a custom scrollbar with letters and numbers, while scrolling the scrollbar with thumb, alphabets or numbers appear beside thumb.I have attached screenshot to the question of the scrollbar from the application 'Contacts'.

Screenshot:

So, How to modify a scrollbar in my application which is using recyclerview, to create scrollbar like that scrollbar with the alphabet and number bubble or is there any new API or library introduced for that?

As I can understand from your question, you want to implement the "Fast Scroll" feature in Android.

This feature lets you quickly scroll through a large list. You can easily implement it using this third-party library.

Its very simple, light-weight and is highly customization too. Don't underestimate it by looking at the screenshot above. You can easily make it look like the screenshot you provided. I used it sometime back in one of my apps and got excellent results.

Usage

Using this library is also simple. You just need to include its QuickScroll layout and implement the Scrollable interface on your BaseAdapter. Giving this widget the Material look-and-feel is really simple.

Update

Due to user demand, for all those who want to know how to use "Fast Scroll" feature in RecyclerView, here it is for you all. You can use this library.

It can give you results which is very close (if not exact) to the screenshot provided. You just have to use RecyclerViewFastScroller widget in your layout.